Problem: $-\dfrac{7}{8} - \dfrac{6}{2} = {?}$
$ = - {\dfrac{7 \times 1}{8 \times 1}} - {\dfrac{6 \times 4}{2 \times 4}} $ $ = - {\dfrac{7}{8}} - {\dfrac{24}{8}} $ $ = - \dfrac{{7} - {24}}{8} $ $ = -\dfrac{31}{8}$